1. Field of the Invention
This invention relates to scroll fluid apparatus suitable for use as compressors, expanders, liquid pumps, etc. and, more particularly, to an oil feeding device for the scroll fluid apparatus of the aforementioned type.
2. Description of the Prior Art
A scroll fluid apparatus of the type disclosed, for example, in U.S. Pat. No. 3,884,599 usually comprises an orbiting scroll member including an end plate, and a wrap in the form of an involute or any other curve similar thereto which is located on the end plate in upstanding position; a fixed scroll member including an end plate, a wrap in the form of an involute or any other curve similar thereto which is located on the end plate in upstanding position, and a discharge port formed in the end plate; a housing formed with a suction port and containing the orbiting scroll member and the fixed scroll member maintained in pressing engagement with each other at the surface of the respective end plates with the wraps facing inwardly against the end plates of the opposed scroll members; an Oldham's ring interposed between the orbiting scroll member and the housing or the fixed scroll member for preventing the rotation of the orbiting scroll member on its own axis; and a crankshaft maintained in engagement with the orbiting scroll member to enable the orbiting scroll member to move in orbiting movement by the action of the crankshaft while the orbiting scroll member does not rotate apparently on its own axis, whereby the fluid within sealed spaces defined by the two scroll members can be allowed to perform a pumping action or a pressure fluid can be supplied through the discharge port to expand the pressure fluid to cause a drive force for rotating the crankshaft to be generated.
In scroll fluid apparatus of the aforementioned type, the crankshaft is usually of a vertical type and its shaft portion is journaled by two plain bearings or upper and lower plain bearings while its crank portion is in engagement with a plain bearing mounted at the orbiting scroll member. Oil feeding devices for feeding lubricating oil to the plain bearings journaling the shaft portion of the vertical crankshaft are disclosed, for example, in U.S. Pat. No. 4,065,279 and Japanese patent Application Laid-Open No. 125386/80. The oil feeding devices of the prior art disclosed in these documents include oil feeding grooves extending along the axis of the shaft portion or the crank portion. One disadvantage of the oil feeding devices of the prior art referred to hereinabove would appear to be the lack of ingenuity in design with which each bearing is caused to generate an oil film reaction capable of coping with a load applied on the bearing by the fluid pressure in the sealed spaces defined by the two scroll members and by the tilting of the crankshaft in the bearings.